Lighting problem

I did an Easter shoot this weekend and I took a picture of this family and for some reason the lighting was off and it not only made the picture grainy but it also is really hard for me to lighten and get it looking right...can anyone help with this?http://www.jenniferowensphotography.com/IMG_8379.jpg

Here's a quick before & after of the results I got with just a Curves adjustment, I've also attached a snapshot of what the curve looked like. You lose some detail in the highlights (some in the sky but most importantly on the ladies' dresses), so if you are going to go the curves route you should probably use a Curves adjustment layer so you can control what areas the adjustment affects and how great of an effect it has.